Short answer. The shortfall you promised. Under Article 1858, a limited partner is liable to the partnership for the difference between what he actually contributed and what the certificate states he contributed, and for any future contribution he agreed in the certificate to make. These liabilities can be waived only by the consent of all members.
What the law says
For the difference between his contribution as actually made and that stated in the certificate as having been made
Civil Code, Article 1858 — Limited Partner's Liability to the Partnership. Read the full provision →
You owe what the certificate says you contributed
Article 1858 makes a limited partner liable to the partnership on two counts tied to the contribution the certificate records. First, for the difference between his contribution as actually made and that stated in the certificate as having been made — so if the certificate says you put in more than you really did, you owe the gap. Second, for any unpaid contribution which he agreed in the certificate to make in the future at the time and on the conditions stated in the certificate — a promised future contribution is a real debt, due when the certificate says.
Property wrongly returned is held in trust
The article also treats a limited partner as a trustee for the firm in two situations where value that should be the partnership's ends up in his hands. He holds as trustee specific property stated in the certificate as contributed by him, but which was not contributed or which has been wrongfully returned, and money or other property wrongfully paid or conveyed to him on account of his contribution. So if the certificate says you contributed a particular thing that you never actually handed over, or that was later given back to you improperly, you hold it for the partnership — it is not truly yours.
Waiver, and the creditor's override
These liabilities are not something the partners can quietly release among themselves to a creditor's detriment. The article provides they can be waived or compromised only by the consent of all members — and even then, a waiver shall not affect the right of a creditor who extended credit, or whose claim arose, after the certificate was filed and before it was cancelled or amended, to enforce the liabilities. The article adds a further reach: a limited partner who has rightfully received back his capital is still liable, up to the amount returned with interest, for sums needed to pay creditors whose claims arose before the return.
If you underpaid or got money back
If you are a limited partner who never paid in full what the certificate records, treat the shortfall as a genuine debt to the partnership — it can be enforced, and a creditor who relied on the certificate can enforce it even if the other partners would let you off. The same goes for a future contribution you promised in the certificate: it comes due on the stated terms. And if you have had capital returned, be aware it is not necessarily safe in your hands — you can be required to give it back, up to that amount with interest, to pay creditors whose claims predate the return.