https://skillhammer.com/posts/ Short, practical posts from SkillHammer. en-gb Wed, 28 Oct 2026 00:00:00 +0000 https://skillhammer.com/posts/quickbooks-requestid-duplicate-invoices/https://skillhammer.com/posts/quickbooks-requestid-duplicate-invoices/Wed, 28 Oct 2026 00:00:00 +0000A timed-out create can still succeed in QuickBooks Online. Send a stable requestid on every write so a retry returns the original instead of a second invoice. https://skillhammer.com/posts/stripe-final-notice-next-payment-attempt/https://skillhammer.com/posts/stripe-final-notice-next-payment-attempt/Tue, 27 Oct 2026 00:00:00 +0000Don't decide a failed payment is the last one by counting attempts. Check the invoice's next_payment_attempt instead. https://skillhammer.com/posts/n8n-approval-links-get-safe/https://skillhammer.com/posts/n8n-approval-links-get-safe/Mon, 26 Oct 2026 00:00:00 +0000Email scanners and chat link previews open links on their own. If an n8n approval link acts on GET, approval can fire before anyone reads it. https://skillhammer.com/posts/stripe-out-of-order-subscription-events/https://skillhammer.com/posts/stripe-out-of-order-subscription-events/Sun, 25 Oct 2026 00:00:00 +0000Stripe doesn't promise to deliver webhook events in order, so an older customer.subscription.updated can undo a newer one. Here's a simple guard. https://skillhammer.com/posts/quickbooks-invalid-grant-refresh-token/https://skillhammer.com/posts/quickbooks-invalid-grant-refresh-token/Sat, 24 Oct 2026 00:00:00 +0000QuickBooks Online refresh tokens can rotate when you refresh. Save the new one every time, and refresh once per company, or you'll get invalid_grant. https://skillhammer.com/posts/stripe-webhook-signature-errors-express/https://skillhammer.com/posts/stripe-webhook-signature-errors-express/Fri, 23 Oct 2026 00:00:00 +0000Two common causes of Stripe's "No signatures found matching the expected signature" error in Express, and how to fix each.