Jurisprudence holds that the right to appeal is neither a natural right nor a part of due process; it is merely a statutory privilege, and may be exercised only in the manner and in accordance with the provisions of law. (Fenequito v. Vergara Jr., G.R. No. 172829, 18 July 2012). An appeal being a purely statutory right, an appellant or appealing party must strictly comply with the requisites in the Rules of Court.

With respect to ordinary appealed cases to the Court of Appeals (CA), Section 7, Rule 44 of the Revised Rules of Civil Procedure requires an appellant to file an Appellant's Brief with the CA within 45 days from receipt of the notice of the clerk.

According to the Supreme Court in Philippine Coconut Authority v. Corona International Inc. (G.R. No. 13991, 29 September 2000), the purpose of the Appellant's Brief is to present to the court in coherent and concise form the point and questions in controversy and by fair argument on the facts and law of the case, to assist the court in arriving at a just and proper conclusion.

Failure to file an Appellant's Brief within the prescribed period is a ground for the dismissal of the appeal. (Section 1(e), Rule 50 of the Revised Rules)
However, the SC clarified in Sindophil Inc. v. Republic (G.R. No. 204594, 07 November 2018) that the use of the permissive "may" in the wording of the above-stated provision means the dismissal of an appeal by the CA is directory and not mandatory.

This means that the failure to file an appellant's brief within the reglementary period would not automatically result in the outright dismissal of the appeal, as the CA is bound to exercise its sound discretion whether to allow the appeal to proceed or not.

The SC explained that allowing the appeal despite the failure to file an Appellant's Brief must be decided by the CA, taking into account all the factors surrounding the case. Its discretion must be exercised with due regard to justice and fair play under the circumstances.

In several cases, the question of whether or not to sustain the dismissal of an appeal due to the appellant's failure to file the Appellant's Brief had been raised before the SC. In some of these cases, the High Court relaxed the Rules and allowed the belated filing of the Appellant's Brief. In other cases, however, the Court applied the Rules strictly and considered the appeal abandoned, which thus resulted in its eventual dismissal.

Finally, in Government of the Kingdom of Belgium v. Court of Appeals (G.R. No. 164150, 14 April 2008), the SC revisited the cases that it had previously decided and laid down the following guidelines in confronting the issue of non-filing of the Appellant's Brief:

1. The general rule is for the CA to dismiss an appeal when no appellant's brief is filed within the reglementary period prescribed by the rules;
2. The power conferred upon the CA to dismiss an appeal is discretionary and directory and not ministerial or mandatory;
3. The failure of an appellant to file his brief within the reglementary period does not have the effect of causing the automatic dismissal of the appeal;
4. In case of late filing, the appellate court has the power to still allow the appeal; however, for the proper exercise of the court's leniency[,] it is imperative that:
(a) the circumstances obtaining warrant the court's liberality;
(b) that strong considerations of equity justify an exception to the procedural rule in the interest of substantial justice;
(c) no material injury has been suffered by the appellee by the delay;
(d) there is no contention that the appellee's cause was prejudiced; or
(e) at least there is no motion to dismiss filed.
5. In case of delay, the lapse must be for a reasonable period; and
6.Inadvertence of counsel cannot be considered as an adequate excuse to call for the appellate court's indulgence except:
(a) where the reckless or gross negligence of counsel deprives the client of due process of law;
(b) when application of the rule will result in outright deprivation of the client's liberty or property or
(c) where the interests of justice so require.