I missed an increase three rounds ago. Can I fix it without undoing?

Work a make-one: insert the hook under the horizontal bar that lies between the current stitch and the one before it, twist it slightly so it forms a loop, and work a sc into that loop. That adds a stitch without needing to go back.

Place it directly above the missing increase rather than at the current count's expected position. The point is to restore the column of stitches where the shaping needs it, not to make today's round add up.

Undo if the missing stitch is on the visible right side of an unstuffed piece — a bag, a hat, a flat motif. An injected stitch in an unstuffed fabric sits slightly differently from its neighbours and shows in raking light, and there is nowhere for it to hide.

Undo if more than six rounds have passed. Six rounds of a 6-point schedule is six missing stitches, and six injected stitches in a row produce a visible ridge of their own. Below three rounds it is almost always worth a patch; above six it almost never is.

Missed increases almost always happen in the same place: the last increase of a round, two stitches before the join, where attention is already on the join. Put a marker in the first stitch of every increase round and, when you reach it again, check the count before continuing.

For 6-point rounds, count out loud in sixes as you work. Six is a small enough group to hold in working memory, and hearing the number land wrong is more reliable than seeing it.