diff --git a/src/components/companies/company-form.tsx b/src/components/companies/company-form.tsx
new file mode 100644
index 0000000..6bd3104
--- /dev/null
+++ b/src/components/companies/company-form.tsx
@@ -0,0 +1,262 @@
+'use client';
+
+import { useEffect, useState } from 'react';
+import { useForm } from 'react-hook-form';
+import { zodResolver } from '@hookform/resolvers/zod';
+import { useMutation, useQueryClient } from '@tanstack/react-query';
+import { Loader2 } from 'lucide-react';
+import { z } from 'zod';
+
+import { Button } from '@/components/ui/button';
+import { Input } from '@/components/ui/input';
+import { Label } from '@/components/ui/label';
+import { Textarea } from '@/components/ui/textarea';
+import {
+  Select,
+  SelectContent,
+  SelectItem,
+  SelectTrigger,
+  SelectValue,
+} from '@/components/ui/select';
+import { Sheet, SheetContent, SheetFooter, SheetHeader, SheetTitle } from '@/components/ui/sheet';
+import { Separator } from '@/components/ui/separator';
+import { TagPicker } from '@/components/shared/tag-picker';
+import { apiFetch } from '@/lib/api/client';
+import { createCompanySchema, type CreateCompanyInput } from '@/lib/validators/companies';
+
+type CompanyStatus = 'active' | 'dissolved';
+
+type CompanyFormValues = z.input<typeof createCompanySchema>;
+
+interface CompanyFormProps {
+  open: boolean;
+  onOpenChange: (open: boolean) => void;
+  /** If provided, form is in edit mode */
+  company?: {
+    id: string;
+    name: string;
+    legalName: string | null;
+    taxId: string | null;
+    registrationNumber: string | null;
+    incorporationCountry: string | null;
+    incorporationDate: string | null;
+    status: string;
+    billingEmail: string | null;
+    notes: string | null;
+  };
+}
+
+export function CompanyForm({ open, onOpenChange, company }: CompanyFormProps) {
+  const queryClient = useQueryClient();
+  const isEdit = !!company;
+  const [formError, setFormError] = useState<string | null>(null);
+
+  const {
+    register,
+    handleSubmit,
+    watch,
+    setValue,
+    reset,
+    formState: { errors, isSubmitting },
+  } = useForm<CompanyFormValues>({
+    resolver: zodResolver(createCompanySchema),
+    defaultValues: {
+      name: '',
+      status: 'active',
+      tagIds: [],
+    },
+  });
+
+  const tagIds = watch('tagIds') ?? [];
+  const status = watch('status') ?? 'active';
+
+  // Populate form when editing, or reset to defaults in create mode.
+  useEffect(() => {
+    if (company && open) {
+      reset({
+        name: company.name,
+        legalName: company.legalName ?? undefined,
+        taxId: company.taxId ?? undefined,
+        registrationNumber: company.registrationNumber ?? undefined,
+        incorporationCountry: company.incorporationCountry ?? undefined,
+        incorporationDate: company.incorporationDate
+          ? new Date(company.incorporationDate)
+          : undefined,
+        status: (company.status as CompanyStatus) ?? 'active',
+        billingEmail: company.billingEmail ?? undefined,
+        notes: company.notes ?? undefined,
+        tagIds: [],
+      });
+    } else if (!company && open) {
+      reset({ name: '', status: 'active', tagIds: [] });
+    }
+    setFormError(null);
+  }, [company, open, reset]);
+
+  const mutation = useMutation({
+    mutationFn: async (data: CreateCompanyInput) => {
+      if (isEdit) {
+        // updateCompanySchema omits tagIds — strip them from PATCH body.
+        const { tagIds: _tIds, ...rest } = data;
+        void _tIds;
+        await apiFetch(`/api/v1/companies/${company!.id}`, {
+          method: 'PATCH',
+          body: rest,
+        });
+      } else {
+        await apiFetch('/api/v1/companies', { method: 'POST', body: data });
+      }
+    },
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['companies'] });
+      onOpenChange(false);
+    },
+    onError: (err: unknown) => {
+      const msg = err instanceof Error ? err.message : 'Failed to save company';
+      setFormError(msg);
+    },
+  });
+
+  return (
+    <Sheet open={open} onOpenChange={onOpenChange}>
+      <SheetContent className="w-full sm:max-w-2xl overflow-y-auto">
+        <SheetHeader>
+          <SheetTitle>{isEdit ? 'Edit Company' : 'New Company'}</SheetTitle>
+        </SheetHeader>
+
+        <form
+          onSubmit={handleSubmit((data) => {
+            setFormError(null);
+            mutation.mutate(data as CreateCompanyInput);
+          })}
+          className="space-y-6 py-6"
+        >
+          {/* Basics */}
+          <div className="space-y-4">
+            <h3 className="text-sm font-medium text-muted-foreground uppercase tracking-wide">
+              Basics
+            </h3>
+
+            <div className="grid grid-cols-2 gap-4">
+              <div className="col-span-2 space-y-1">
+                <Label>Name *</Label>
+                <Input {...register('name')} placeholder="Acme Holdings Ltd" />
+                {errors.name && <p className="text-xs text-destructive">{errors.name.message}</p>}
+              </div>
+
+              <div className="col-span-2 space-y-1">
+                <Label>Legal Name</Label>
+                <Input {...register('legalName')} placeholder="Acme Holdings Limited" />
+              </div>
+            </div>
+          </div>
+
+          <Separator />
+
+          {/* Registration */}
+          <div className="space-y-4">
+            <h3 className="text-sm font-medium text-muted-foreground uppercase tracking-wide">
+              Registration
+            </h3>
+            <div className="grid grid-cols-2 gap-4">
+              <div className="space-y-1">
+                <Label>Tax ID</Label>
+                <Input {...register('taxId')} placeholder="VAT / EIN" />
+              </div>
+              <div className="space-y-1">
+                <Label>Registration Number</Label>
+                <Input {...register('registrationNumber')} placeholder="Company #" />
+              </div>
+              <div className="space-y-1">
+                <Label>Incorporation Country</Label>
+                <Input {...register('incorporationCountry')} placeholder="e.g. MT" />
+              </div>
+              <div className="space-y-1">
+                <Label>Incorporation Date</Label>
+                <Input type="date" {...register('incorporationDate')} />
+                {errors.incorporationDate && (
+                  <p className="text-xs text-destructive">{errors.incorporationDate.message}</p>
+                )}
+              </div>
+            </div>
+          </div>
+
+          <Separator />
+
+          {/* Contact & Status */}
+          <div className="space-y-4">
+            <h3 className="text-sm font-medium text-muted-foreground uppercase tracking-wide">
+              Contact & Status
+            </h3>
+            <div className="grid grid-cols-2 gap-4">
+              <div className="space-y-1">
+                <Label>Billing Email</Label>
+                <Input
+                  type="email"
+                  {...register('billingEmail')}
+                  placeholder="billing@example.com"
+                />
+                {errors.billingEmail && (
+                  <p className="text-xs text-destructive">{errors.billingEmail.message}</p>
+                )}
+              </div>
+              <div className="space-y-1">
+                <Label>Status</Label>
+                <Select
+                  value={status}
+                  onValueChange={(v) => setValue('status', v as CompanyStatus)}
+                >
+                  <SelectTrigger>
+                    <SelectValue placeholder="Select status" />
+                  </SelectTrigger>
+                  <SelectContent>
+                    <SelectItem value="active">Active</SelectItem>
+                    <SelectItem value="dissolved">Dissolved</SelectItem>
+                  </SelectContent>
+                </Select>
+              </div>
+            </div>
+          </div>
+
+          <Separator />
+
+          {/* Notes */}
+          <div className="space-y-2">
+            <Label>Notes</Label>
+            <Textarea
+              {...register('notes')}
+              placeholder="Internal notes about this company"
+              rows={4}
+            />
+          </div>
+
+          <Separator />
+
+          {/* Tags */}
+          <div className="space-y-2">
+            <Label>Tags</Label>
+            <TagPicker selectedIds={tagIds} onChange={(ids) => setValue('tagIds', ids)} />
+          </div>
+
+          {formError && (
+            <p className="text-sm text-destructive" role="alert">
+              {formError}
+            </p>
+          )}
+
+          <SheetFooter>
+            <Button type="button" variant="outline" onClick={() => onOpenChange(false)}>
+              Cancel
+            </Button>
+            <Button type="submit" disabled={isSubmitting || mutation.isPending}>
+              {(isSubmitting || mutation.isPending) && (
+                <Loader2 className="mr-2 h-4 w-4 animate-spin" />
+              )}
+              {isEdit ? 'Save Changes' : 'Create Company'}
+            </Button>
+          </SheetFooter>
+        </form>
+      </SheetContent>
+    </Sheet>
+  );
+}